This invention relates generally to a discharge assembly for material ground by attrition in a rotating mill. More particularly, the present invention provides an improved discharge assembly constructed from a plurality of sections which protect the mill from wear caused by ground material being discharged from the mill.
Grinding mills for grinding materials such as ore are well known in the art. The mills include a substantially cylindrical shell that rotates about a longitudinal axis. The shell includes lifting members facing the interior of the shell that lift the ore about the inner periphery surface toward the top of the shell when the shell is rotating. Gravity then causes the ore to tumble toward the bottom of the shell where it is reduced in size by impact with pieces of ore, lifter members or steel charge. In an autogenous grinding method, the ore is its own grinding media, whereas in a semi-autogenous method, a mixture of ore and steel charge is used to facilitate grinding.
Ore material is fed into the enclosure and ground by comminution to a desired size. After the ore is reduced to a desired size, the ore enters a plurality of discharge passageways formed in a discharge assembly through grates located at the periphery of the discharge assembly. The discharge assembly is positioned at an end opposite the feed end of the mill about a discharge trunnion and centered on the mill axis. As the shell rotates, the ground ore is transported towards the rotating axis of the shell for discharge from the mill through the discharge trunnion.
Commonly, a replaceable tubular insert is positioned in each of the discharge passageways to line the passageway and increase life by protecting the passageway from the abrasive ground ore. However, like all components located in the mill, the inserts are subject to wear from the abrasive nature of the ground ore, and thus, are susceptible to collapse, which would block the discharge passageway. Also, additional energy is required to operate the mill since the inserts add significantly to the overall weight of the mill.
In an effort to eliminate inserts, fabricated discharge assemblies were constructed wherein passageways were formed using components placed against each other in a radial fashion. However, such constructions allow ground material to leak from the chute and become located between the discharge assembly components and the mill shell. Undesirable wear occurs on the mill due to leakage of the abrasive ground materials between the components.